Retrieveing path of text files in Directory using Java

Even though this is not an optimum solution you can use this as a starting point.

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DirectoryWalker {

    /**
     * @param args
     */
    private String extPtr = "^.+\\.txt$";
    private Pattern ptr;
    public DirectoryWalker(){
        ptr = Pattern.compile(extPtr);
    }
    public static void main(String[] args) {
        String entryPoint = "c:\\temp";
        DirectoryWalker dw = new DirectoryWalker();
        List<String> textFiles  = dw.extractFiles(entryPoint);
        for(String txtFile : textFiles){
            System.out.println("File: "+txtFile);
        }
    }

    public List<String> extractFiles(String startDir) {

        List<String> textFiles = new ArrayList<String>();

        if (startDir == null || startDir.length() == 0) {
          throw new RuntimeException("Directory entry can't be null or empty");
        }

        File f = new File(startDir);
        if (!f.isDirectory()) {
          throw new RuntimeException("Path " + startDir + " is invalid");

        }

        File[] files = f.listFiles();
        for (File tmpFile : files) {
            if (tmpFile.isDirectory()) {
                textFiles.addAll(extractFiles(tmpFile.getAbsolutePath()));
            } else {
                String path = tmpFile.getAbsolutePath();
                Matcher matcher = ptr.matcher(path);
                if(matcher.find()){
                    textFiles.add(path);
                }
            }
        }

        return textFiles;
    }
}

Create a File object representing the directory, then use one of the list() or listFiles() methods to obtain the children. You can pass a filter to these to control what is returned.

For example, the listFiles() method below will return an array of files in the directory accepted by a filter.

public File[] listFiles(FileFilter filter)

Start by reading the File API. You can create a File from a String and even determine if it exists() or isDirectory(). As well as listing the children in that directory.